/* S0440.java 
 *        アーラン乱数の発生 
 *         (C) H.Ishikawa 2008 
 */

package simulation;

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import window.Window;

public class S0440 extends Applet implements ActionListener {
	Button button0;
	public void init() {
		button0 = new Button(" 再実行 ");
		add(button0);
		button0.addActionListener(this);
	}
	
	public void actionPerformed(ActionEvent e) {
		String label = e.getActionCommand();
		repaint();
	}

	public void paint(Graphics g){

		Window w ;
		w = new Window();
		int NUMBER  =    1000;
		int SIZE =   20;               /* ヒストグラムの大きさ */
		double KIZAMI =  0.2;          /* 0.2ずつに区切ってヒストグラムへ */
		int j;                          /* forのカウンタ */
		int u;                          /* キザミの番号 */
		int i;                          /* forのカウンタ */
		int f[] = new int[SIZE];       /* 頻度 */
		int k = 1;                      /* 位相 k=1,2,4,8,16 */
		double lambda = 1;              /* λ */  
		
		/* グラフィックの準備 */
		int SPACE = 40;
		int HIGHT = 640;
		int WIDTH = 640;
  
		w.setWindow(0,  0.0,0.0,4.001,0.4,SPACE,HIGHT/5-SPACE,WIDTH-SPACE,0);
		w.axis(0, "", 0.2, "k = 1", 0.1,g);
		w.setWindow(1,  0.0,0.0,4.001,0.4,SPACE,2*HIGHT/5-SPACE,WIDTH-SPACE,HIGHT/5);
		w.axis(1, "", 0.2, "k = 2", 0.1, g);
		w.setWindow(2,  0.0,0.0,4.001,0.4,SPACE,3*HIGHT/5-SPACE,WIDTH-SPACE,2*HIGHT/5);
		w.axis(2, "", 0.2, "k = 4", 0.1,g);
		w.setWindow(3,  0.0,0.0,4.001,0.4,SPACE,4*HIGHT/5-SPACE,WIDTH-SPACE,3*HIGHT/5);
		w.axis(3, "", 0.2, "k = 8", 0.1,g);
		w.setWindow(4,  0.0,0.0,4.001,0.4,SPACE,HIGHT-SPACE,WIDTH-SPACE,4*HIGHT/5);
		w.axis(4, "", 0.2, "k = 16", 0.1,g);

		/* メイン */
		for (i = 0; i < 5; i ++) {
			for (j = 0; j < NUMBER; j++) {
				u = (int)(erlang(lambda, k) / KIZAMI);
				if (u < SIZE) {f[u] = f[u] + 1;}
		    }
			/* ヒストグラムを書く */
			g.setColor(Color.red);
			for (u = 0; u < SIZE; u ++) {
				w.line(i, (u+0.5) * KIZAMI, 0, (u+0.5) * KIZAMI, (double)f[u] / NUMBER, g);
				f[u] = 0;
			}
			k = k * 2;   /* 2倍のkの値で続ける */
		}
	}
	double erlang(double lambda, int k){
		double tp = 1.0;
		double tau;
		int n;
		for (n = 1; n <= k; n ++) {
			tp = tp * (1 - Math.random());
		}
		tau = -1.0 / lambda / (double)k * Math.log(tp);
		return (tau);
	}
}